Try again: Check blockfile size before attempting to read the header.

net/disk_cache/block_files.h

Index: net/disk_cache/block_files.h
diff --git a/net/disk_cache/block_files.h b/net/disk_cache/block_files.h
index 790cc7d4f45446f372c7fd545f2927a30bd36998..e86546eb98076382607f840119190e808154e46e 100644
--- a/net/disk_cache/block_files.h
+++ b/net/disk_cache/block_files.h
@@ -11,6 +11,7 @@
 
 #include "net/disk_cache/addr.h"
 #include "net/disk_cache/mapped_file.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
 
 namespace disk_cache {
 
@@ -75,6 +76,8 @@ class BlockFiles {
   std::wstring path_;  // Path to the backing folder.
   std::vector<MappedFile*> block_files_;  // The actual files.
 
+  FRIEND_TEST(DiskCacheTest, BlockFiles_ZeroSizeFile);
+
   DISALLOW_EVIL_CONSTRUCTORS(BlockFiles);
 };